Democrats have flipped the panic switch in Massachusetts, setting off an eleventh-hour effort to lock up what they have repeatedly called “Ted Kennedy’s seat” in the Senate.

In latest sign of just how worried Democrats are, a leaked memo written by Coakley’s finance chairman and sent to top donors on Tuesday warned of a “very tight” race and made an “urgent” appeal for supporters to “max out” donations at $2,400 each. This after the Democratic Senatorial Campaign Committee injected nearly $600,000 into the race and as the DNC is poised to spend an additional $500,000.

The memo concedes that national conservative groups have effectively mobilized for Brown, and acknowledges that the Coakley campaign is “having trouble moving independents.”

Money spent of Brown’s behalf by such groups as the U.S. Chamber of Commerce and Club for Growth “seems to be working,” the memo says, adding that “Polling shows that Republican voters are more energized than Democrats.”

“We have a battle on our hands,” the memo concludes.

Even as it fights to fatten its bankroll, the Coakley campaign is turning up the campaign rhetoric.

A new attack ad labels Brown a “lockstep” Republican while juxtaposing photos of him with a crying rape victim and an image of Rush Limbaugh executing what appears to be a Nazi salute.

An e-mail from Sen. John Kerry (D., Mass.) to Democratic supporters warns of Browns “allies in the right wing” who “dream of holding a ‘tea party’ in Kennedy country”—an awkward analogy since the original tea party was held in Boston Harbor.

And on Monday, a top DNC aide sent a series of emails soliciting Sarah Palin to weigh-in on Brown’s candidacy, an apparent effort to draw the hitherto silent former Alaska governor, a polarizing figure among independents, into the race to Coakley’s presumed benefit.

President Obama has so far limited his campaigning on Coakley’s behalf to e-mail solicitations, but there is speculation that a senior administration official—perhaps the president himself, or Vice-President Joe Biden—could travel to to Massachusetts if the race remains close down the stretch.

If all else fails and Coakley loses, Democrats are prepared to delay credentialing Brown until after a final vote on a merged House-Senate health-care bill. The Senate majority has signaled it would not seat a victor in the special election without formal certification from Massachusetts’s top election official, Democrat William Galvin, a process that would give Senate Democrats at least ten days after the start of their 2010 legislative session to pass a bill with interim Senator Paul Kirk (D., Mass.) in place as a 60th vote.